Prismatic Triangular Background Design Mark II 5 #406
 Dark  CC 0

Prismatic Triangular Background Design Mark II 5

Source GDJ

 More Textures
Diamonds Are Forever@2X #184
 Diamond  CC BY-SA 3.0

Sharp diamond pattern. A small 24x18px tile.

Source Tom Neal

Prismatic Abstract Geometric Background 4 #271
 Noise  CC 0

Prismatic Abstract Geometric Background 4

Source GDJ

Background pattern 21 #205
 Light  CC 0

A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.

Source Firkin

Background pattern 308 (colour 4) #1868
 Green  CC 0

Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.

Source Firkin

Starring #585
 Dark  CC BY-SA 3.0

If you need stars, this is the one to get.

Source Agus Riyadi

Transparent Square Tiles #298
 Grid  CC BY-SA 3.0

The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.

Source Nathan Spady

Diagonal Noise #181
 Fabric  CC BY-SA 3.0

A simple but elegant classic. Every collection needs one of these.

Source Christopher Burton

Batthern@2X #325
 Grid  CC BY-SA 3.0

Sometimes simple really is what you need, and this could fit you well.

Source Factorio.us Collective

Prismatic Polka Dots Mark II 2 No Background #532
 Noise  CC 0

Prismatic Polka Dots Mark II 2 No Background

Source GDJ

Prismatic Curved Diamond Pattern 4 No Background #541
 Diamond  CC 0

Prismatic Curved Diamond Pattern 4 No Background

Source GDJ

Prismatic Abstract Geometric Background 4 No Black #441
 Dark  CC 0

Prismatic Abstract Geometric Background 4 No Black

Source GDJ